Mycoplasma pneumoniae is a leading atypical cause of community-acquired pneumonia in children and adults, and the prevalence of resistance to macrolides, the recommended first-line agents, varies markedly by region. Since the fastidious growth of M. pneumoniae makes phenotypic antimicrobial susceptibility testing impractical for routine use, clinical microbiology laboratories have focused on 23S rRNA gene-targeted molecular detection. This mini-review examines the molecular mechanisms of macrolide resistance, laboratory detection strategies, global epidemiology, and clonal dynamics revealed by molecular typing. Macrolide resistance is primarily driven by point mutations in domain V of the 23S rRNA gene, with A2063G accounting for most mutations worldwide, and A2064G being reported less frequently. Resistance in Korea rose from 2.9% in 2003 to 87.2% in a 2015 pediatric cohort, with subsequent studies reporting persistently high rates of approximately 78-87%. Earlier molecular typing studies suggest that this high resistance burden has been associated, at least in part, with the expansion of sequence type (ST) 3 and ST14 lineages. In contrast, Japan and Taiwan showed sharp declines following reductions in macrolide prescribing and P1 genotype turnover. Following the COVID-19 pandemic, a strong resurgence centered in East Asia, the possible global dispersal of ST3 and ST14 to Australia, Iran, and Canada, and the impact of co-circulation with influenza H3N2 have been reported. Real-time polymerase chain reaction (PCR) with simultaneous detection of 23S rRNA gene mutations and targeted metagenomic sequencing are emerging as next-generation surveillance tools. In summary, clinical microbiology laboratories should integrate M. pneumoniae detection with 23S rRNA gene resistance mutation detection using molecular assays and strengthen typingbased surveillance, thereby responding actively to the changing dynamics in East Asia and contributing to antimicrobial stewardship.
Background: Environmental contamination with multidrug-resistant organisms (MDROs), including carbapenem-resistant Acinetobacter baumannii (CRAB) and multidrug-resistant Pseudomonas aeruginosa (MRPA), remains a major challenge in healthcare facilities. Hypochlorous acid water (HOCl) has emerged as a promising disinfectant owing to its strong antimicrobial activity and favorable safety profile. This study aimed to evaluate the bactericidal efficacy of atomized HOCl against CRAB and MRPA in a hospital room. Methods: An atomization experiment was conducted in a two-bed room. CRAB and MRPA were prepared using drying and non-drying methods, respectively. HOCl (CLFine) at concentration of 40 and 300 ppm was atomized using ultrasonic humidifiers. Bacterial samples were collected at 0, 1, 3, and 5 h after atomization. Viable bacterial counts were determined by culture, and bactericidal efficacy was evaluated. Results: Atomized HOCl exhibited time- and concentration-dependent bactericidal effects against CRAB and MRPA. CRAB and MRPA reached their limits of detection at 3 and 5 h post-atomization at 40 ppm, and at 1 and 3 h at 300 ppm, respectively. Conclusion: Atomized HOCl effectively inactivated CRAB and MRPA in a hospital room within 3–5 h. These findings support the potential application of HOCl atomization as an adjunctive environmental disinfection strategy for controlling MDRO contamination in healthcare facilities.
Background: Pathogenic Escherichia coli (PEC) is a leading cause of acute diarrhea worldwide. With increasing antibiotic use, antimicrobial resistance in PEC has become a significant public health concern. In this study, we investigated the distribution and antimicrobial susceptibility patterns of PEC isolated from patients with acute diarrhea in the Busan and Gyeongnam regions of South Korea. Methods: In this retrospective cross-sectional laboratory-based study, 272 PCR-positive residual stool or rectal swab specimens collected between October 2023 and June 2024 were screened; after exclusion of 80 specimens without recoverable or confirmable isolates, 192 pathogenic E. coli isolates were included for pathotype identification and antimicrobial susceptibility testing. Pathotypes were identified using multiplex real-time polymerase chain reaction, and antimicrobial susceptibility was tested against 18 agents using the VITEK II system. Results: Enteroaggregative E. coli (EAEC) was the most prevalent pathotype (44.8%), followed by enteropathogenic E. coli (34.9%). High resistance rates were observed for ampicillin (77.1%), cefazolin (55.2%), and amoxicillin/clavulanic acid (44.3%). EAEC demonstrated the highest multidrug resistance (MDR) rate (34.9%). Pediatric patients (< 18 years) exhibited significantly higher resistance rates and MDR frequencies compared with adults, particularly against β-lactam antibiotics. Conclusion: EAEC was identified as the predominant and most resistant pathotype in this region. The elevated resistance levels in children and the prevalence of MDR EAEC underscore the need for continuous local surveillance and appropriate antibiotic stewardship.
Background: Enzyme immunoassays (EIAs), which detect glutamate dehydrogenase (GDH) and toxin A/B, are widely used to screen for Clostridioides difficile infection (CDI); however, their sensitivity is lower than that of molecular assays. This study aimed to evaluate the performance of two EIAs, C. Diff Quik Chek Complete (QCC) and RIDASCREEN (RIDA), and investigate the cycle threshold (Ct) values from two real-time polymerase chain reaction (PCR) assays (Allplex GI–Bacteria(I) and Xpert C. difficile) in EIA-discordant samples. Methods: A total of 180 clinical stool samples were tested using QCC, RIDA, and Allplex GI-Bacteria(I) PCR assays. The Xpert C. difficile assay was used to analyze discordant results. Results: QCC and RIDA showed high sensitivities for GDH detection, 100.0% and 94.4%, respectively. QCC was significantly more sensitive than RIDA for toxin detection (51.4% vs. 28.6%, p = 0.007). In 25 EIA-discordant, Xpert positive samples, the Ct values of the toxin B gene ranged from 31.5 to 44.8 (mean, 38.1) for Allplex PCR and from 23.7 to 36.3 (mean, 30.4) for Xpert PCR. The Ct values of the two PCR assays were not significantly correlated (r = 0.201, p = 0.324). Conclusion: QCC is a suitable initial immunological test for diagnosing CDI. The lack of correlation in the Ct values between the two real-time PCR assays suggests that assay-specific validation is necessary for cutoff level interpretation.
Background: The accurate laboratory-based detection of respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is essential for effective patient management and infection control in the post–coronavirus disease 2019 era. In this study, the performance of the PowerChek Respiratory Virus Panels 1–4 assay (Kogene Biotech) in detecting non-SARS-CoV-2 respiratory viruses and SARS-CoV-2 was compared with those of two established commercial assays. Methods: Residual clinical respiratory specimens collected between December 2023 and February 2024 were retested using the PowerChek assay. Of the 129 specimens retested, 80 had tested positive for 14 non-SARS-CoV-2 respiratory virus targets in the Allplex Respiratory Panels 1–3 assay (Seegene) and 49 had been tested using the Alinity m SARS-CoV-2 assay (Abbott; 20 positive and 29 negative for SARS-CoV-2). Agreement, Cohen’s kappa, and discordant results were assessed. Results: For the 14 non-SARS-CoV-2 respiratory virus targets, the virus-specific overall percent agreement (OPA) ranged from 95.0% to 100%, the positive percent agreement (PPA) ranged from 66.7% to 100%, and the negative percent agreement (NPA) ranged from 96.0% to 100%, with kappa values of 0.64–1.00. Lower agreements were observed for human coronavirus OC43 and influenza A virus. For SARS-CoV-2 detection, the OPA was 98.0% (PPA, 95.0%; NPA, 100%; kappa, 0.96). Conclusion: The detection performance of the PowerChek assay was comparable to those of the established assays for most respiratory virus targets, with lower agreement observed for some targets. These features support its practical utility for the routine multiplex molecular detection of respiratory viruses, including SARS-CoV-2.
Tuberculosis (TB) remains a major global health threat, and the emergence and spread of drug-resistant Mycobacterium tuberculosis continue to undermine control efforts. Multidrug-resistant and rifampicin-resistant TB (MDR/RR-TB) is associated with prolonged treatment, higher toxicity, increased costs, and poorer outcomes compared to susceptible TB, making rapid and accurate drug susceptibility testing (DST) essential for effective patient management and transmission prevention. This review summarizes the current methods for DST in TB, focusing on the principles, strengths, and limitations of phenotypic and molecular approaches. Phenotypic DST, including the proportion, absolute concentration, and resistance ratio methods, and automated liquid culture systems, remains the conventional reference standard; however, conventional methods are limited by long turnaround times and technical complexity for certain drugs (such as pyrazinamide). Molecular DST targets resistance-associated mutations in key genes and is represented by line probe assays and cartridge-based platforms such as the Xpert MTB/RIF, which provide rapid results but are restricted to predefined genetic loci and may exhibit discordance with phenotypic DST, particularly with regard to borderline resistance. Next-generation sequencing (NGS)-based assays, including whole-genome sequencing and targeted NGS panels, offer comprehensive resistance profiling with high diagnostic accuracy and are increasingly being incorporated into international guidelines. Finally, we discuss the clinical interpretation of discordant results between genotypic and phenotypic DST, the impact of revised rifampicin critical concentrations, and the integration of DST results into contemporary World Health Organization guidelines and Korean treatment recommendations for MDR/RR-TB. Informed, methodologically grounded use of DST is crucial for optimizing the diagnosis and management of drug-resistant TB.
Background: Mycobacterium avium complex (MAC) is a major cause of pulmonary nontuberculous mycobacterial disease; however, treatment outcomes remain suboptimal. Phenotypic drug susceptibility testing (DST) is conditionally recommended; however, conventional broth microdilution is labor-intensive. The Sensititre SLOMYCO® panel offers a standardized platform for DST of slowly growing mycobacteria. Methods: Eighty-six clinical MAC isolates (48 M. avium and 38 M. intracellulare) from respiratory specimens were tested for 13 antimicrobials using the SLOMYCO panel and reference Clinical and Laboratory Standards Institute (CLSI) broth microdilution methods at the Korean Institute of Tuberculosis. Essential agreement (EA) was defined as minimum inhibitory concentrations within ± 1 dilution, and categorical agreement (CA) was based on CLSI 2018 breakpoints for clarithromycin, amikacin, moxifloxacin, and linezolid. Results: The EA was high for amikacin (90%), moxifloxacin (92%), linezolid (92%), and ethambutol (98%). Moderate EA was observed for clarithromycin (79%), ciprofloxacin (67%), and doxycycline (63%), and low EA was observed for trimethoprim-sulfamethoxazole (34%). The CA values were 100%, 77.9%, 69.8%, and 47.7% for clarithromycin, amikacin, moxifloxacin, and linezolid, respectively. All isolates were clarithromycin-susceptible according to both methods, and no clarithromycin- or amikacin-resistant isolates were detected. Conclusion: The SLOMYCO DST system demonstrated high agreement with the reference methods for clarithromycin and amikacin in the tested susceptible population. The variability in the results for moxifloxacin and linezolid highlights the need for refined breakpoints. The validation of resistant isolates is essential before the SLOMYCO system can be recommended for comprehensive clinical applications.
Background: Human metapneumovirus (hMPV) is a major cause of acute respiratory infections in children and adults worldwide; however, no antiviral therapies or vaccines are currently available. Therefore, rapid and reliable diagnostic tools are required to support timely patient management and control outbreaks. Methods: We retrospectively evaluated GenBody hMPV Ag Rapid Test results using 165 consecutive clinical samples collected from patients with suspected respiratory infections between May and August 2024. Specimens were pre-characterized using a confirmatory reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay. Diagnostic performance was summarized using percent positive agreement (PPA), percent negative agreement (NPA), and overall percent agreement (OPA), with subgroup analyses by age and cycle threshold (Ct) groups. Results: The GenBody assay achieved a PPA of 92.7% (51/55), NPA of 100% (110/110), and OPA of 97.6% (161/165), with no false-positive results. Age-stratified analysis showed high PPA in infants (93.3%) and children (97%), whereas estimates in hMPV-positive adolescents (n = 2) and adults (n = 5) were less precise owing to the small sample size. In the Ct-stratified analysis, PPA was 100% for specimens with Ct ≤ 28 (39/39), whereas all false-negative results occurred in the Ct > 28 group (12/16). Conclusion: In this retrospective, single-center evaluation, the GenBody hMPV Ag Rapid Test showed high agreement with RT-qPCR, with reduced detection in specimens with higher Ct values. Further prospective studies and long-term stability assessments are warranted to confirm the performance across a broader range of clinical settings and storage conditions.
Background: Haemophilus influenzae is the causative pathogen for various infectious diseases, such as respiratory infections, otitis media, sinusitis, and meningitis. This study aimed to investigate the prevalence and molecular characteristics of β-lactam resistance in non-typeable H. influenzae isolates in South Korea. Methods: In total, 115 non-duplicated H. influenzae isolates were included in this study. Bacterial identification and serotyping were performed using matrix-assisted laser desorption ionization-time of flight mass spectrometry and polymerase chain reaction (PCR) of bexA, respectively. Antimicrobial susceptibility was tested using the broth microdilution method. The production of β-lactamase was determined using nitrocefin disks. The presence of blaTEM and blaROB was confirmed using PCR. ftsI was analyzed to identify amino acid mutations in penicillin-binding protein (PBP) 3. Results: Resistance rates to ampicillin, amoxicillin–clavulanate, and cefuroxime were 67.8%, 13.9%, and 32.2%, respectively. None of the isolates were resistant to cefotaxime or ceftriaxone. Among 78 ampicillin-resistant isolates, 71 were β-lactamase-producing ampicillin-resistant (BLPAR), and 7 were β-lactamase-non-producing ampicillin-resistant. All BLPAR isolates carried blaTEM, and none carried blaROB. Among 16 amoxicillin–clavulanate-resistant isolates, 15 β-lactamase producers harbored blaTEM. Four to 7 PBP3 mutations per isolate were detected in all 16 non-β-lactamase-producing ampicillin-resistant or cephalosporin-resistant isolates. Conclusion: β-lactam resistance in non-typeable H. influenzae isolates is highly prevalent in South Korea, primarily because of blaTEM and various PBP3 mutations. Therefore, continuous monitoring of antimicrobial resistance rates and mechanisms in non-typeable H. influenzae is necessary.
In the present review, we systematically examine the diverse applications of whole-genome sequencing (WGS) and next-generation sequencing (NGS) to elucidate the evolution of clinical microbiology. The review aims to provide novel insight and to improve understanding of the applications of WGS in clinical microbiology laboratories. It is organized into the following sections: (1) the various types of NGS machines; (2) NGS workflows for obtaining genome sequences; (3) comparative genomic analysis; (4) RNA-seq (transcriptome) analysis; (5) genome-based bacterial typing; (6) genome-based antimicrobial resistance (AMR) detection; and (7) identification of integrative and conjugative elements carrying AMR gene(s). Four figures and three tables are provided to illustrate this information. The discussion focuses on WGS applications using several genera of microorganisms (Streptococcus, Enterococcus, Staphylococcus, Pasteurella, and Mycobacterium). Overall, WGS and related NGS technologies provide innovative clinical microbiology laboratory studies based on high-throughput genomic results for pathogen identification, tracking, and AMR/virulence profiling. In line with the concept of “One Health,” human and animal microbiology laboratories should pay careful attention to the drastically dynamic evolution of WGS and related NGS technologies.
Background: The growing burden of nontuberculous mycobacteria (NTM) raises concerns regarding cross-reactivity in molecular tuberculosis (TB) diagnostics. In the current study, we evaluated whether high NTM loads affect Mycobacterium tuberculosis (MTB) detection or rifampin (RIF) resistance calls using Xpert MTB/RIF (Xpert) and Xpert MTB/RIF Ultra (Xpert Ultra). Methods: In vitro spiking experiments were performed by mixing eight NTM species (1 × 106 colony-forming unit [CFU]/mL) with heat-inactivated MTB (RIF-susceptible H37Rv; RIFresistant S450L) at 5 × 103 CFU/mL in pooled smear-negative sputum, before testing them in parallel using Xpert and Xpert Ultra. We also retrospectively analyzed 334 results from lower respiratory specimens, including 32 NTM-positive specimens tested using both assays, and assessed the presence of probe amplification in the NTM-confirmed specimens. Results: In spiking experiments, both assays showed no NTM-related cross-reactivity: RIFsusceptible mixes were “RIF resistance not detected,” S450L mixes were correctly resistant with preserved mutant melt peaks, and MTB-specific cycle threshold and melting peak temperature profiles were unchanged by NTM. Of the 334 clinical specimens, NTM was isolated from 32. Xpert classified all 32 as MTB-negative, and Xpert Ultra classified 31 of 32 as MTB-negative and one as “very low” positive in a patient with prior TB, consistent with residual nonviable DNA. In NTM-positive, Xpert/Xpert Ultra-negative specimens, neither assay showed probe amplification. Conclusion: High-burden NTM did not compromise MTB detection or RIF-resistance determination using Xpert or Xpert Ultra. The assays demonstrated robust analytical specificity in mixed MTB–NTM contexts, supporting their use where NTM carriage is common.
Background: Diagnostic tests are essential for accurate disease identification and monitoring treatment responses. This study aimed to assess the factors influencing the requests for microbial diagnostic tests in patients with various infections. Methods: Using tailored data from the National Health Insurance Big Data, we examined the usage patterns of microbiological tests among patients with pulmonary tuberculosis (TB) and major bacterial infections between 2020 and 2022, excluding overlapping and complex infections (n = 8,268,992). The types of bacterial infections included pneumonia, sepsis, urinary tract infections, and soft tissue infections, for which bacterial culture and antimicrobial susceptibility tests were performed. For pulmonary TB cases, acid-fast bacillus smears, mycobacterial cultures, and molecular diagnostic tests were performed. Multivariate analysis was used to identify the factors influencing the prescription of microbiological diagnostic tests, considering variables such as age, sex, Charlson comorbidity index, underlying disease, type of medical institution, residential area, insurance quintile, and disability status. Results: Requests for TB-related and bacterial infection-related tests varied according to multiple factors, including sex, age, insurance quintile, residential area, presence or absence of disability, disease severity, type of medical institution admission, chemotherapy, steroid use, comorbid conditions, and underlying diseases. Conclusions: This study is considered to be rare data analyzed using large-scale national data on various factors affecting test prescriptions, which could provide useful data for improving policies for appropriate test prescriptions.
Latent tuberculosis (TB) refers to a state in which an individual is infected with Mycobacterium tuberculosis but shows no clinical symptoms. The World Health Organization estimates that 23% of the global population has latent TB, which poses a significant public health challenge owing to the risk of progression to active TB. Diagnosis of latent TB involves tests, such as the tuberculin skin test (TST) and interferon-gamma release assays (IGRAs). The TST can yield false positives due to prior Bacillus Calmette-Guérin (BCG) vaccination, whereas IGRAs offer higher specificity and are unaffected by BCG vaccination. Factors, such as age and recent vaccinations, can affect test performance. Treatment with isoniazid and rifampicin is recommended for those diagnosed, as it has been shown to prevent 80%-90% of active TB cases, although more extended follow-up studies are needed to confirm its long-term efficacy. Indeterminate IGRA results, especially in immunocompromised individuals, add complexity to the diagnosis and treatment decisions, highlighting the need for careful interpretation. Further research is vital to improve the diagnostic accuracy, interpretation, and treatment effectiveness.
Accurate identification of the Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM) is crucial for effective patient management. With declining tuberculosis and rising NTM infections in South Korea, rapid diagnostics are essential. This review provides a comprehensive overview of current diagnostic methods for mycobacterial identification used in Korean clinical laboratories. The field has shifted from conventional methods, such as acid-fast bacilli staining, culture, and biochemical tests, toward rapid technologies. In Korea, immunochromatographic assays (ICA) targeting the MPT64 antigen are widely used to differentiate MTBC from NTM. For species-level NTM identification, laboratories employ advanced techniques including mycolic acid analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and diverse molecular assays. Prominent molecular diagnostics include real-time PCR, PCR-restriction fragment length polymorphism (RFLP), line probe assays (LPA), and DNA sequencing of genes like 16S rRNA and rpoB. These modern techniques offer significantly improved speed and accuracy, replacing traditional approaches in routine diagnostics. In South Korea, modern tools have supplanted conventional methods for mycobacterial identification. Real-time PCR and antigen detection are the primary assays for identifying MTBC in cultures. For NTM species, laboratories use a range of techniques including PCR-RFLP, HPLC, LPA, MALDITOF MS, and sequencing. Next-generation sequencing is poised to become a pivotal future tool, offering comprehensive species identification and simultaneous profiling of drug resistance. Those modern techniques will transform diagnostic and surveillance strategies for mycobacterial diseases.
Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM) present distinct clinical and epidemiological challenges and thus require tailored genotyping approaches. MTB is a globally transmissible pathogen for which diagnostic and surveillance infrastructures are well defined, whereas NTM infections are environmentally acquired, taxonomically diverse, and increasingly prevalent among vulnerable populations. Molecular genotyping is indispensable for both pathogen groups, supporting outbreak investigation and drug resistance prediction for MTB and species-level identification and relapse-versusreinfection distinction for NTM. In this review, the evolution of strategies for genotyping mycobacteria are outlined, and traditional techniques (e.g., spoligotyping and mycobacterial interspersed repetitive unit–variable number tandem repeat genotyping) and advanced methods (multilocus sequence typing and whole-genome sequencing) are compared. We highlight the divergent drivers of genotyping between MTB and NTM, examine key technical and interpretive challenges, and discuss how cross-learning between these two fields can accelerate innovation. Emerging technologies such as portable sequencing platforms, artificial intelligence-assisted analysis, and curated genomic databases are expanding access to high-resolution genotyping. However, significant gaps remain, particularly in standardizing NTM genomic analyses and integrating genotypic data into global surveillance systems. By exploring the intersections between MTB and NTM molecular epidemiology, a synergistic pathway for more precise, accessible, and effective mycobacterial genotyping is highlighted.
Background: Accurate diagnosis of Clostridioides difficile infection (CDI) requires both microbiologic confirmation and clinical correlation. Current guidelines recommend a two-step algorithm combining a sensitive screening test with a specific confirmatory assay. This study evaluated the diagnostic performance of the glutamate dehydrogenase (GDH)/toxin enzyme immunoassay (EIA) over five years and assessed its suitability as an initial screening test. Methods: We retrospectively analyzed 8,685 C. difficile-related tests conducted between March 2020 to February 2025. The GDH/toxin EIA was performed using the C. DIFF QUIK CHEK COMPLETE (TechLab). Toxigenic culture involved alcohol-shocked stool samples plated on chromogenic agar and incubated anaerobically for 48 hours. Toxin gene polymerase chain reaction (PCR) was done using the BD MAX Cdiff assay and the Xpert C. difficile assay. Results: The GDH test showed a sensitivity of 77.0% and negative predictive value (NPV) of 95.1% compared with culture. The toxin EIA showed 35.0% sensitivity and 96.9% positive predictive value relative to PCR. The combined GDH+Toxin EIA achieved 82.6% sensitivity and 96.9% NPV compared with PCR. Most discordant results involved low bacterial burden or non-toxigenic isolates. GDH positivity correlated with growth quantity, and toxin EIA positivity varied by ribotype. Algorithm modeling suggested the GDH/toxin test as a cost-effective firstline option. Conclusion: The GDH/toxin EIA demonstrated high NPV and may be appropriate as an initial test in CDI diagnostic algorithms. These findings support its role in diagnostic stewardship and provide evidence to inform the development of national diagnostic guidelines in Korea.
Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for various clinical infections. The investigation of representative MRSA genomes is important for understanding their molecular epidemiology and genetic evolution, as well as MRSA infections. We characterized the complete genome sequences of representative MRSA clinical strains prevalent in Korea between 2014 and 2017. Methods: Ten representative clinical MRSA strains were selected based on the staphylococcal cassette chromosome mec (SCCmec) type. Complete genomes were generated via hybrid assembly using long- and short-read sequencing. Analyses of resistance and virulence genes, whole-genome alignment, phylogenetic tree construction, and comparative genome hybridization were performed. Results: The average chromosomal lengths were 2.916 Mb in SCCmec II (n = 6), 2.920 Mb in SCCmec IV (n = 2), and 2.777 Mb in SCCmec IVA (n = 2). The number of genome coding sequences ranged from 2,713 to 3,026, with an average of 2,946 in SCCmec II, 3,001 in SCCmec IV, and 2,740 in SCCmec IVA. Only the SCCmec IV and spa t008 strains (n = 2) harbored the Panton–Valentine leukocidin gene, which is rarely detected in Korea. The SCCmec IVA strains of ST72 showed a distinct genetic group compared with other representative SCCmec IV strains, as determined by single-nucleotide polymorphism analysis. Conclusion: In the present study, the complete and gap-filled genome sequences of representative MRSA clones prevalent in Korea were derived and characterized by genome size, virulence, antimicrobial resistance genes, and their evolutionary relationships. Information on these clinical MRSA strains would enhance our understanding of the pathogenicity and molecular epidemiology of Korean MRSA isolates.
Background: Haemophilus is an important pathogen in community-acquired pneumonia and invasive diseases, such as sepsis and meningitis. We aimed to evaluate the VITEK 2 system and VITEK MS system for the identification of Haemophilus strains isolated from clinical specimens in Korea during 2023. Methods: In total, 118 Haemophilus strains isolated from respiratory specimens (n = 107) and blood samples (n = 11) from 10 sentinel hospitals in Kor-GLASS were included in this study. All Haemophilus strains were evaluated using the VITEK 2 and VITEK MS systems. Real-time PCR and 16S rRNA sequencing were used to identify specific species. Results: Among the 118 Haemophilus isolates, 115 were identified as H. influenzae by realtime PCR using hpd gene, and the remaining three strains were identified as H. parainfluenzae by 16S rRNA sequencing. Eighty-eight of the 115 (76.5%) and two of three (66.7%) isolates were correctly identified as H. influenzae and H. parainfluenzae, respectively, using the VITEK 2 system. The VITEK 2 system showed low discrimination (n = 22), misidentification (n = 4), and unidentified organisms (n = 2) in the 28 Haemophilus strains. The VITEK MS system achieved 100% sensitivity and specificity in identifying all 115 H. influenzae and three H. parainfluenzae isolates. Conclusion: The VITEK MS system showed excellent performance in the identification of H. influenzae and H. parainfluenzae, whereas the VITEK 2 system showed relatively low concordance.
